Proof: Collinear Angles Property 8
Let's prove the following theorem:
if m∠ABC = 180, then m∠XAB = m∠XAC
Proof:
Given
| 1 | m∠ABC = 180 |
|---|
| # | Claim | Reason |
|---|---|---|
| 1 | m∠CBA = 180 | if m∠ABC = 180, then m∠CBA = 180 |
| 2 | m∠BAX = m∠CAX | if m∠CBA = 180, then m∠BAX = m∠CAX |
| 3 | m∠BAX = m∠XAB | m∠BAX = m∠XAB |
| 4 | m∠XAB = m∠CAX | if m∠BAX = m∠XAB and m∠BAX = m∠CAX, then m∠XAB = m∠CAX |
| 5 | m∠CAX = m∠XAC | m∠CAX = m∠XAC |
| 6 | m∠XAB = m∠XAC | if m∠XAB = m∠CAX and m∠CAX = m∠XAC, then m∠XAB = m∠XAC |
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